Effect of fermentation on apparent total and nutrient digestibility of linseed, Linum usitatissimum, meal in rohu, Labeo rohita, fingerlings

Plant oilseeds and their by-products usually constitute a major source of dietary protein in feeds of warm water omnivorous/herbivorous fish species (Lim and Dominy 1991). Some of the factors which limit application of these ingredients in fish feeds at high levels include low protein content, amino-acid imbalance, and the presence of antinutritional factors (Wee 1991). In India, the digestibility of locally available feed ingredients has been a subject of a few studies, conducted on carp (Jayaram and Shetty 1980, Ray and Das 1994, Mukhopadhyay and Ray 1997). Linseed meal is often used as a dietary ingredient in fish feed. Hasan et al. (1989) used linseed meal as a feed ingredient in the diet of walking catfish, Clarias batrachus, fry. Hasan et al. (1991) used it successfully in the diet of Labeo rohita. Hossain and Jauncey (1989) studied the protein, energy content, and amino acid digestibility of linseed meal. The low apparent protein digestibility of linseed might be due to the presence of mucilage in it. In addition, Hossain and Jauncey (1989) investigated the nutritive value of linseed meal of Bangladeshi origin and tested it in a diet of common carp, Cyprinus carpio. Earlier, studies on the digestibility of an ingredient usually involved the reference diet to the ingredient ratio of 7 : 3 ratio (Cho et al. 1974). De Silva et al. (1990), however, have shown that a desirable proportion of the ingredient relative to the reference diet should vary from 80%–85% to 20%–15%. In this study, an attempt was made to evaluate the suitability of incorporating raw and fermented linseed meal ACTA ICHTHYOLOGICA ET PISCATORIA (2005) 35 (2): 73–78